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fs/proc/task_mmu.c: simplify m_start() to make it readable 

Now that m->version is gone we can cleanup m_start(). In particular,

  - Remove the "unsigned long" typecast, m->index can't be negative
    or exceed ->map_count. But lets use "unsigned int pos" to make
    it clear that "pos < map_count" is safe.

  - Remove the unnecessary "vma != NULL" check in the main loop. It
    can't be NULL unless we have a vm bug.

  - This also means that "pos < map_count" case can simply return the
    valid vma and avoid "goto" and subsequent checks.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2014-10-09 15:25:36 -07:00 committed by Linus Torvalds
parent ebb6cdde1a
commit 0c255321f8
1 changed files with 10 additions and 24 deletions
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34
fs/proc/task_mmu.c
View File

@ -138,12 +138,12 @@ static void vma_stop(struct proc_maps_private *priv)
mmput(mm);
}
static void *m_start(struct seq_file *m, loff_t *pos)
static void *m_start(struct seq_file *m, loff_t *ppos)
{
struct proc_maps_private *priv = m->private;
struct mm_struct *mm;
struct vm_area_struct *vma, *tail_vma = NULL;
loff_t l = *pos;
struct vm_area_struct *vma;
unsigned int pos = *ppos;
priv->task = get_pid_task(priv->pid, PIDTYPE_PID);
if (!priv->task)
@ -152,33 +152,19 @@ static void *m_start(struct seq_file *m, loff_t *pos)
mm = priv->mm;
if (!mm || !atomic_inc_not_zero(&mm->mm_users))
return NULL;
down_read(&mm->mmap_sem);
tail_vma = get_gate_vma(mm);
priv->tail_vma = tail_vma;
hold_task_mempolicy(priv);
priv->tail_vma = get_gate_vma(mm);
/*
* Check the vma index is within the range and do
* sequential scan until m_index.
*/
vma = NULL;
if ((unsigned long)l < mm->map_count) {
vma = mm->mmap;
while (l-- && vma)
if (pos < mm->map_count) {
for (vma = mm->mmap; pos; pos--)
vma = vma->vm_next;
goto out;
return vma;
}
if (l != mm->map_count)
tail_vma = NULL; /* After gate vma */
out:
if (vma)
return vma;
if (tail_vma)
return tail_vma;
if (pos == mm->map_count && priv->tail_vma)
return priv->tail_vma;
vma_stop(priv);
return NULL;